Spark plug



J. GRANT SPARK PLUG Sept. 6, 1938.,

Filed Aug. 22, 1936 TYJ.

/NVENTo/e dan/15J G/eAA/T @Y r /fff Patented Sept. 6, 1938 UNirE srAr 1 Claim.

My invention relates to improvements in spark plugs and an object of the invention is to provide a device of the character herein described which will permit the length of the spark gap thereof to be easily and conveniently adjusted without removing the plug from its position in the engine.

A further object of the invention is to provide a device of the character herein described in which the sparking surfaces of both the electrodes have a considerable area which increases the eifective life of the spark plug by prolonging the time necessary for the plug to become carbonized.

A still further object of the invention is to provide a device of the character herein described which is simple to construct and economical to manufacture.

With the above more important objects in view and such other minor objects as may appear as the specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawing, in which:-

Fig. l illustrates a central sectional elevation of my improved type of spark plug.

Fig. 2 shows a view of the lower end of the same.

In the drawing like characters of reference indicate corresponding parts in the different figures.

It is well known that for efficient performanceI of internal combustion engines, the length of the gap in the spark plugs has to be adjusted to suit the conditions existing in various types of engines. For instance, in an engine in which the compression is relatively low, the spark gap should be about one half as wide again as in the case of an engine in which the compression is high. Also the correct adjustment of the spark gap in automobiles vvill generally result in more efficient performance and will aid in reducing misring of the cylinders.

Hitherto, adjustment of the spark gaps in englues of this type has required that in each case, the spark plug be removed and the gap adjusted by bending one of the electrodes slightly. This method, however, has been found ineffectual as a considerable amount of experiment is necessary to obtain the correct gap length.

The spark plug herein described, however, can be easily adjusted without removing it from its socket.

This invention consists of a metallic shell l which is outwardly threaded at 2 for attachment to the cylinder head. The shell is provided with a socket 3 therein, which is reduced to form a shoulder 4 from the inner edge of which extends a downwardly flared portion 5.

Into the socket 3 is inserted the usual core 6 composed of porcelain, mica, or other insulating (Cl. l23--169) material. This core is held iirmly in position by a bushing l which is threadably received by the upper part of the socket 3.

A passageway 8 extends longitudinally through the center of the core and is reduced in diameter 5 and threaded as at 9. An electrode I0 is passed through the passageway and is threadably received by the portion 9. The upper end of the electrode is also threaded to receive the locking nut ll and a knurled terminal nut l2. 10

To the lower end of the electrode is an integrally attached circular metallic spider I 3 whichconsists of a wire ring it, held in position by a plurality of radially extending spokes l5.

With this arrangement, it will be obvious that 15 if the nut ll is loosened slightly, the electrode l0 can be rotated to thread through the portion 9 of the core. This will change the position of the spider i3 in the ilared end of the spark plug and 'will, accordingly, increase or decrease the dis- 20 tance between the outer edge of the ring I4 and the flared wall.

The use of the ring It, it should be noted, provides a large area from which the spark may leap, and if one portion thereof should become cor- 25 roded or carbonized, instead of the spark plug ceasing to operate, the discharge will merely take place across fromn another portion of the spider and the plug will thus continue to function.

It will therefore be apparent that I have pro- 30 vided a simple yet ingenious method of varying the discharge gap of a spark plug and at the same time, produced a device which possesses an inherently long life.

Since various modications can be made in the above invention and many apparently widely different embodiments of same, made within the scope of the claim without departing from the spirit and scope thereof, it is intended that all matter contained in the accompanying speciflca- 40 tion shall be interpreted as illustrative only and not in a limiting sense and I desire only such limitations placed thereon as are specifically expressed in the accompanying claim.

What I claim as my invention is:- 45

A spark plug for internal combustion engines comprising a metallic shell having a socket therein, an insulating core, a flared passageway having a smooth surface within said shell communicating with said socket, an electrode extending through 50 said core and into said passageway, a circular member attached to said electrode within said passageway and concentric therewith, said electrode being threadably received by said core, permitting manual end-shifting thereof to vary the 55 gap length between the surface of said passageway and said circular member.

JAMES GRANT. 

